How to reference a class that implements certain interface?

Question

I have an interface for logging the exceptions, i.e. IExceptionLogger.

This interface has 3 implementations: DBExceptionLogger, XMLExceptionLogger, CSVExceptionLogger.

I have an application that will make a use of DBExceptionLogger.

The application references only IExceptionLogger. How do I create an instance of DBExceptionLogger within the application.

I can't reference the DBExceptionLogger directly since it will break the purpose of having IExceptionLogger interface.

Answer 1

//Usage of logger with factory
IExceptionLogger logger = ExceptionLoggerFactory.GetLogger();

public static class ExceptionLoggerFactory
{
  public static IExceptionLogger GetLogger()
  {
    //logic to choose between the different exception loggers
    //e.g.
    if (someCondition)
      return new DBExceptionLogger();
    //else etc etc 
  }
}